1. Field
Aspects of the present disclosure relate generally to spectral color reproduction, and more particularly, to spectral color reproduction using a high-dimension reflective display.
2. Background
Interferometric modulator display (IMOD), is a technology used in electronic visual displays that can create various colors via interference of reflected light. The color is selected with an electrically switched light modulator comprising a microscopic cavity that is switched on and off using driver integrated circuits similar to those used to address liquid crystal displays (LCD). An IMOD-based reflective flat panel display includes hundreds of thousands of individual IMOD elements, each one a microelectromechanical systems (MEMS)-based device.
Each IMOD pixel selectively absorbs and/or reflects light using the principles of optical interferometric absorption. An IMOD display element may include a pair of conductive plates, one of which has a high reflectance and one is partially absorptive. The position of one plate in relation to another can change the spectrum of the reflected light from the IMOD display element. The gap between two plates is sometime called air-gap. If the air-gap of each pixel can be dynamically changed, the IMOD display is called analog IMOD display or AiMOD (Analog Interferometric Modulation) display. The number of primaries is determined by the available positions (air-gaps) configured for the device. When not being addressed, an IMOD display consumes very little power. Unlike conventional back-lit liquid crystal displays, the IMOD is clearly visible in bright ambient light such as sunlight.
Each basic element of an AiMOD-based display changes reflective color spectrum independently by changing the air-gap. Depending on the spectrum it reflects and/or absorbs, the primary can be white, black, or a color. Each of white, black, or a color is named a primary. Each pixel is capable of changing from one primary color to another, but it is not able to change the brightness level. Elements are organized into a rectangular array in order to produce a display screen.
As each element reflects only a certain amount of light, grouping several elements of the same color together as subpixels allows different brightness levels for a pixel based on how many elements are reflective at a particular time. Multiple color displays are created by using subpixels, each designed to reflect a specific different color. Multiple elements of each color are generally used to both give more combinations of displayable color (by mixing the reflected colors) and to balance the overall brightness of the pixel. Another approach to produce multi-levels of brightness is to use temporal modulation and/or spatial dithering.
Because elements only use power in order to switch among primary states (no power is needed to reflect or absorb light hitting the display once the element is either reflecting or absorbing), IMOD-based displays potentially use much less power than displays that generate light and/or need constant power to keep pixels in a particular state. Being reflective displays, they require an external light source (such as daylight or a lamp) to be readable, just like paper or other electronic paper technologies.
Most current displays use colorimetric color characterization, which produce colors to match original colors colorimetrically. Such a display, which is calibrated to produce colorimetric colors under an illuminant, is not suitable for spectral reproduction. In the color characterization for AiMOD displays, the illuminant dependency is revealed. This illuminant dependency is a more serious problem in a reflective display than in an emissive display (e.g., LCD display).